Glow plug construction

ABSTRACT

A GLOW PLUG HAS A TUBULAR CASING THROUGH WHICH EXTENDS IN INSULATED RELATIONSHIP A HELIX CONSTITUTED BY AN ELECTRICALLY CONDUCTIVE TUBULAR MEMBER. IN THE REGION OF ONE END OF THE CASING THE TUBULAR MEMBER HAS AN INLET FOR COMBUSTIBLE FUEL FLUID, AND IN THE REGION OF THE OTHER END IT HAS ONE OR MORE OUTLETS. THE TUBULAR MEMBER IS CONNECTED WITH A SOURCE OF ELECTRICAL ENGERGY WHICH HEATS IT SO THAT WHEN FLUID PASSES THROUGH THE TUBULAR MEMBER, IT WILL ISSUE AT THE OUTLER AS A VAPOR. A PAIR OF ELECTRODES ARE PROVIDED DEFINING IN THE REGION OF THE OUTLET A HIGHVOLTAGE SPARK GAP FOR IGNITING THE ISSUING VAPOR.

H. WEYL ET AL Feb. 27, 1973 2 Sheets-Sheet 1 Filed Marh 5, 1972 Feb. 27, 1973 H. wEYL ETAL 3,718,425

GLOW PLUG CONS'IIUCTlON Filed March 5, 1972 2 Sheets-Sheet 2 Fig. 3

United States Patent O 3,718,425 GLOW PLUG CONSTRUCTION Helmut Weyle, Bietigheim, Gunther Kauhl, Asperg, and Otto Beesch, Stuttgart, Germany, assignors to Robert Bosch G.m.b.H., Stuttgart, Germany Filed Mar. 3, 1972, Ser. No. 231,607 Claims priority, application Germany, Mar. 17, 1971,

Int. Cl. F2341 11/44 U.S. Cl. 431-208 8 Claims ABSTRACT OF THE DISCLOSURE A glow plug has a tubular casing through which extends in insulated relationship a helix constituted by an electrically conductive tubular member. In the region of one end of the casing the tubular member has an inlet for combustible fuel fluid, and in the region of the other end it has one or more outlets. The tubular member is connected with a source of electrical energy which heats it so that when iiuid passes through the tubular member, it will issue at the outlet as a vapor. A pair of electrodes are provided defining in the region of the outlet a highvoltage spark gap for igniting the issuing vapor.

BACKGROUND OF Til-IE 'INVENTION The present invention relates iu general to glow plugs and in particular to an improved glow plug construction.

Glow plugs are used in various applications, including in situations where they serve as a starting aid in diesel and omni-fuel engines. Their purpose is to pre-heat the fuel-air mixture in such engines to a desired temperature, and subsequently to produce a spark which will ignite the thus pre-heated mixture. It will of course be understood that the mixture becomes vaporized as it is being heated.

From U.S. application Ser. No. 139,613, now Pat. No. 3,689,195 (Beesch et al.), it is known to provide such glow plugs in which a helix of electrically conductive tubular material is located in a tubular casing having an inlet in the region of one end of the tubular casing and one or more outlets in the region of the other end thereof. The helix and a central electrode extending through its center and electrically insulated therefrom are mounted in the casing. When a combustible fuel lluid is admitted at the inlet into the tubular member it travels through the convolutions of the same; the tubular member is heated by being connected with a source of electrical energy so that the fuel uid travelling through the convolutions of the tubular member is similarly heated and issues from the outlet as vapor. This vapor is then ignited in the region of the outlet by the center electrode.

The afore-mentioned prior art construction it is possible to reduce pre-heating time, namely the time which must elapse between the initial energization of the glow plug and the initiation of combustion of the issued fuel vapor in the cylinders of an engine, from the previous time of more than 1 minute, to approximately 20 seconds. This means that a diesel or other engine provided with the glow plug according to the prior-art application mentioned above, can be started after a time lapse subsequent to energization of the glow plug which is only approximately one-third as long as was previously required, due to the starting aid derived from the flame which develops on combustion of the vaporized fuel on the glow plug.

However, the reduction in the starting time of an engine provided with such a glow plug is important in many instances. Evidently, in the private sector it is predominantly a matter of convenience, in military ap- 3,718,425 Patented Feb. 27, 1973 plications, however, where diesel-powered armored vehicles or watercraft are frequently employed, this reduction in the required starting time for the engine may also be a matter of safety.

SUMMARY OF THE INVENTION It is a general object of the present invention to provide an improved glow plug construction in which the preheating time :which is required before a diesel or omnifuel engine provided with such a glow plug construction can be started, is further reduced.

A more partic-ular object of the invention is to provide such an improved glow plug construction in which this pre-heating time is reduced to approximately 5-10 seconds.

Another object of the invention is to provide such an improved glow plug construction in which the reliability of ignition in various operating circumstances of the engine is improved.

Still another object of the invention is to provide such a glow plug construction in which the reliability of ignition is improved particularly when there is a strong ow of air in the region where ignition takes place.

In pursuance of these and other objects of the invention which will become apparent hereafter, one feature of the invention resides in a glow plug which, brieliy stated, comprises a tubular casing having two spaced ends and an electrically conductive tubular member forming a helix extending intermediate the ends of the tubular casing longitudinally of the same and having an inlet in the region of one and at least one outlet in the region of the other of said ends. Securing means secure the ltubular member within the casing and supply means is provided for supplying combustible fuel fluid to the interior of the tubular member through the inlet so that the fluid will travel through the member to the outlet thereof. Connecting means is provided for connecting the member with a source of electric energy whereby to heat said member and thereby the iluid travelling therethrough so that the fuel fluid issues from the outlet as a vapor. Finally, there is also provided ignition electrode means which defines in the region of the outlet a spark gap for igniting the issuing vapor.

It is particularly advantageous if the tubular casing is provided at its other end in the region of which the outlet or outlets of the tubular member is located, with a cylindrical protective sleeve secured to the tubular casing and extending forwardly beyond the open end thereof to surround the spark gap and if the circumferential wall of this cylindrical sleeve is provided with windows produced by stamping or punching portions of the wall inwardly of the sleeve so as to form batiles within the latter.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof will be best understood from the following description of specic embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal section through a glow plug according to the present invention;

FIG. 2 is a section taken on line I-I of FIG. 1;

FIG. 3 is a circuit diagram illustrating the electrical connections of the embodiment of FIG. l; and

FIG. 4 is a fragmentary sectional detail view of a detail analogous to FIG. 1, but illustrating a somewhat modi- -iied further embodiment of the invention.

3 DESCRIPTION OF THE PREFERRED EMBODIMENT Discussing firstly the embodiment illustrated in FIGS. 1 3, it will be seen that the novel glow plug is shown as being threadedly secured in an internally tapped socket 101 in the suction manifold 102 of an engine, for instance a conventional diesel engine. The glow plug is retained in its position against displacement by a nut 103.

As shown, the glow plug has a tubular casing 104 prO- vided with an external thread 105 which cooperates with the internal thread in the socket 101. Secured to the end of the casing 104 which in use is located outside the suction manifold 102, for instance by hard soldering, is a connecting member 106 provided with a supply nipple 107 through which combustible fuel fluid is to be supplied to the glow plug. The member 106 also has an electrically conductive, usually metallic, component 109 which is gastightly mounted in a longitudinally extending passage 120 in conventional manner, that is by means of electrically insulating glass melt seal 108. An exposed portion of the component 109 is provided with a connecting member 110 for establishing an electrical connections, for which purpose the member 110 is provided in the illustrated embodiment with a tapped bore 111.

That end ofthe casing 104 which in use extends into the suction manifold 102 is connected with a cylindrical sleeve 112 which is welded to it and extends forwardly beyond it as illustrated. The sleeve is provided with a plurality of windows which are produced in the illustrated embodiments by punching portions of the peripheral wall of the sleeve 112 inwardly so that they constitute turbulence creating mixing baflles 113 and 114 which extend inwardly from the inner surface of the wall of the sleeve 112. It should be noted that the illustrated embodiment the baffles 113 are located closer to the adjacent end of the casing 104 than the baffies 114 and are bent about lines which longitudinally of the axis of the sleeve 112, so that they have planes which extend along this axis, whereas the baffles 114 are bent about lines extending transversely to this axis and accordingly have general planes which also extend transversely to this longitudinal axis. Of course, the bending lines could also be skew with reference to the longitudinal axis and some or all of the baffles could be bent to the exterior rather than the interior of the sleeve 112, just as the baffles 113 and 114 could all be located in a common plane instead of being located in two planes with the bafiies 113 closer to the associated end of the casing 104 than the baffles 114, or the baffles could be located in more than the illustrated two planes.

The component 109 will be seen to have an axially extending passage 116 through which there extend a tube 118 of electrically insulating material, in the illustrated embodiment of ceramic material. The tube 118 is gastightly mounted in the passage 116, again by means of a glass melt seal 119, and projects beyond the passage 116 at one end whereas with its other end it extends into the combustion chamber 117 which is defined by the circumferential wall of the sleeve 112.

A center electrode 121 extends through the tube 118 and has at one end a threaded portion 122; its opposite end extends somewhat beyond the tube 118 to be exposed in the combustion chamber 117. In the illustrated embodiment, the center electrode 121 is secured in the tube 118 by having a portio 124 which is externally tapped and which meshes with an internally tapped section in the interior passage of the tube 118. A flange 123 on the central electrode 121 serves to fix it against axial displacement, and suitable material, such as ceramic or the like, may be employed to seal the electrode in the tube 118 against passage of fluid.

The forward end of the center electrode 121 is exposed in the combustion chamber 117, as already indicated, and in particular, it is located in the region of the baffles 113 and 114. Associated with this forward end of the center electrode 121 is a second electrode 125 which is so spaced from the forward end of the electrode 121 as to define therewith a spark gap 126. The electrode 125 is connected, in the illustrated embodiment by welding with the electrically conductive sleeve 112, and, as the latter is welded to the conductive casing 104 and is thus in conductive relationship with the same, the electrode 125 is in electrically conductive connection with the mass via the suction manifold 102.

The passage of the nipple 107 is to receive combustible fuel Huid from non-illustrated source of supply, and communicates with a bore 127 provided in the element 106. Secured in this bore 127, as by hard soldering, is an open end of a tubular member 128 which is advantageously of chrome-nickel steel, and which is helically convoluted to form the illustrated helix. The helix formed by the tubular member 128 is located within the casing 104 but out of any contact with the same, surrounding the central electrode 121 concentrically. The helix is supported by a ceramic member 129 which is slipped onto a metallic tube 130 surrounding the ceramic tube 118. The member 129 is prevented from axial displacement with reference to the tube 130 by a pair of metallic sleeves or the like 131 which are welded or otherwise secured to the tube 130 at the opposite axial ends of and advantageously in Contact with the member 129.

An end portion of the metallic tube 130 extends into the passage 116 of the member 109 and is secured therein by hard soldering or the like. The length of tube 130 is such that it extends substantially to the region of the combustion chamber 117, that is that it terminates in the vicinity of the open end of the casing 104 where thc sleeve 112 begins. A metallic member 132 surrounds the end portion of the tube 130 in the region of this open end, being connected with the tube 130 by welding or the like, and having an axial bore 133 into which the open outlet end of the tubular member 128 extends being secured therein by hard soldering or the like, so that the open outlet end discharges into the combustion chamber 117. A ceramic sleeve 134 is located in the open end 0f the casing 104, accommodating the member 132 and being connected with the casing 104 in such a manner as to clOse the interior of the casing 104 (where the helix constituted by the tubular member 128 is located) with respect to the combustion chamber 117. The sleeve 134 is in surface-tosurface contact with the member 132.

The circuit diagram -in FIG. 3 illustrating the electrical connection of the illustrated embodiment of FIGS. 1-3, is of course self-explanatory, and it will be appreciated that when for instance a diesel engine is provided with a glow plug according to the present invention land is to be started up, electrical energy-for instance 24 voltsis supplied to the member from it passes via the members 109, 130 and 132 into the tubular member 128. As a result of this, the tubular member, which is connected with mass via members 106, 104 and 102, becomes rapidly heated. Experiments have shown that the tubular member 128 will be sufficiently heated within approximately 4 seconds from the time electrical energy is supplied to it.

It is advantageous to supply combustible fuel fluid via the inlet nipple 107 only after said this period of 4 seconds has elapsed, because this avoids the possibility that non-vaporized liquid fuel fluid might issue from the glow plug and might cause damage to the cylinders and pistons of the engine. The fuel fluid which is supplied via the nipple 107 passes through the convolutions of the helically convoluted tubular member 128 becoming heated due to heat-exchange with the material of the member 128 and becoming vaporized so that -it issues in vaporized form at the outlet end into the combustion chamber 117. In the combustion chamber the vapor becomes admixed with air which enters through the apertures or windows in the sleeve 112. The electrodes 121 and 125 are connected, as also evident from the circuit diagram in FIG. 3, with any high voltage ignition system known per se, which is connected on the one hand with the portion 122 of the electrode 121 and on the other hand with mass, so that a spark will jump the spark gap 126 igniting the volatile-air mixture which is now present in the combustion chamber 117. The admixture of fuel vapor and combustion air in the chamber 117 is facilitated and intensified by the presence of the baffles 113 and 114 which, as the vapor and air pass over them, cause turbulence and consequent rapid and intimate admixture thereof.

In FIG. 4 we have illustrated a further embodiment of the invention. Like reference numerals in FIG. 4 identify components as in FIG. l, and in fact, the construction of the glow plug in FIG. 4 is very similar to that of FIG. 1. The difference in FIG. 4 is that the electrode 125' extends along and in contact with the free end of the ceramic tube 118, in order to provide a path for creepage sparks which are thus enabled to travel between the electrode 125 and the center electrode 121.

The ignition by creepage sparks depends on the construction of the diesel engine and its air intake manifold; the benefit is the desired burning of oil deposits at the electrodes (121, 125').

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions, differing from the types described above.

While the invention has been illustrated and described as embodied in a glow plug, it is not intended to be -limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specic aspects of this invention and therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

We claim:

1. A glow plug, comprising a tubular casing having two spaced ends; an electrically conductive tubular member forming a helix extending intermediate said ends longitudinally of said casing and having an inlet in the region of one and at least one outlet in the region of the other of said ends; securing means securing said tubular member to said casing; supply means for supplying combustible fuel fluid to the interior of said member through said inlet for travel through said member to said outlet;

6 connecting means for connecting said member with a source of electric energy whereby to heat said member and thereby fuel fluid travelling through the same so that such fuel fluid issues from said outlet as a vapor; and ignition electrode means defining in the region of said outlet a spark gap for igniting the issuing vapor.

2. A glow plug as defined in claim 1, said casing being open at said other end; and further comprising a tubular sleeve mounted at said other end and extending forwardly beyond the same and surrounding said spark gap.

3. A glow plug as defined in claim 2, said tubular sleeve having a peripheral wall provided with a plurality of apertures and baie portions extending inwardly of said sleeve from the peripheries of the respective apertures.

4. A glow plug as defined in claim 3, said bae portions being portions of said peripheral wal-l and having general planes at least some of which extend transversely to the longitudinal axis of said sleeve.

5. A glow plug as defined in claim 4, wherein the general planes of others of said baie portions extend longitudinally of said axis.

6. A glow plug as defined in claim 3, said baie portions being portions of said peripheral wall and having general planes at least some of which extend lengthwise of the longitudinal axis of said sleeve.

7. A glow plug as deiined in claim 1, said casing and sleeve being electrical-ly conductive and being conductively connected and wherein said electrode means comprises a center electrode extending axially through said helix in electrically insulated relationship therewith and with said casing, and a cooperating electrode located within and mounted in electrical-ly conductive relationship on said sleeve.

8. A glow plug as delined in claim 1; further comprising a tube of electrically insulating material extending axially through said helix and having an open end located in said sleeve; and wherein said electrode means comprises a center electrode extending through said tube and exposed at said open end thereof, and a cooperating electrode in said sleeve and extending into engagement with said tube in the region of said open end thereof so as to provide a spark gap for creepage sparks.

References Cited UNITED STATES PATENTS 3,353,520 11/1967 Haag 123-179 H 3,614,280 10/1971 Tamio 431-266 EDWARD G. FAVORS, Primary Examiner U.S. Cl. X.R. 

